Prepared by Djamil Fertikh, MD , Mercy Catholic Medical Center, Medical Imaging Department, Darby, PA.

CASE SUMMARY

The patient is a 59-year-old woman who had experienced a fracture of her left proximal femur at age 32. Radiographs revealed a fracture of the femoral neck through an abnormal expansile, ground-glass­like area. A whole-body technetium-99m methylene disphosphonate (MDP) bone scan was performed, showing in addition to the left femur, several areas of abnormal radiotracer uptake, including the left mandible, both humeri, and the left tibia (Figure 1). Magnetic resonance images (MRI) of the right hip were obtained subsequently (Figure 2). Her medical history was significant for precocious puberty, hypothyroidism, and the presence of skin café-au-lait spots.

DIAGNOSIS

Fibrous dysplasia and intramuscular myxomas: Mazabraud's syndrome

IMAGING FINDINGS

Radiographs show ground-glass areas involving the left femur, tibia, and fibula (Figure 3). A whole-body technetium-99m MDP bone scan revealed abnormal areas of radiotracer uptake involving the right proximal femur, the right mandible, both humeri, and the left tibia.

MRI of the patient's left hip showed multiple, well demarcated, intramuscular soft-tissue masses of different sizes, which were characterized by a low signal intensity (SI) on T1-weighted images and a high SI on T2-weighted images (Figure 2).

DISCUSSION

Mazabraud's syndrome is a rare entity represented by the association of fibrous dysplasia and intramuscular myxomas. Their association was first reported in 1957 by A. Mazabraud, a French physican. ¹ Mazabraud's syndrome does not appear to be hereditary and occurs mostly in women. The myxomas tend to develop and congregate around the thighs, buttocks, and shoulder regions. Their neoplastic nature has been questioned over time. Considering their tendency to group close to the affected segments of the bone involved by fibrous dysplasia, they are believed to be a reactive phenomenon due to local mechanical stress factors. Supporting this hypothesis is the fact that, histologically, they appear to be very close to synovial mucoid cysts occurring in stressed articulations. ² Others hypothesize that they may be extraosseous manifestations of fibrous dysplasia. ³ When compared with isolated myxomas, their tendency to reoccur after removal is very low; however, note the postsurgical recurrence in this patient. As in our patient, the polyostotic form of fibrous dysplasia is predominant. Malignant transformation (eg, osteosarcoma, fibrosarcoma) in Mazabraud's syndrome has been reported, but the incidence remains very low. ^2,4 For the myxomas, early surgery is usually advocated, ⁴ since involvement of neurovascular structures in advanced cases renders excisions more laborious.

MRI has been used to evaluate the syndrome. ^5,6 We found it a more useful imaging tool than the CT scan for presurgical evaluation of the anatomy and the extent of the lesion. Awareness of the syndrome and its presentation is essential in distinguishing myxomas from other malignant mesenchyal tumors with myxomal components such as liposarcomas, botyroid-type rhabdomyosarcomas, malignant fibrous histocytomas, extraskeletal chondrosarcomas, and neurofibromatosis, and consequently precluding the need for additional expensive and often stressful investigations.